1. Field of the Invention
The present invention relates to a broadband signal switching device comprising a cross point matrix whose switching elements are respectively controlled by a cross point-associated storage cell selected in two coordinates by two selection decoders.
2. Description of the Prior Art
Recent devleopments in telecommunications technology have lead to service-integrating communications transmission and switching systems for narrow band and broadband communication services which provide light waveguides as transmission media in the area of subscriber lines by way of which both the narrow band communication services such as, in particular, 64 kbit/s digital telephony, as well as broadband communication services such as, in particular, 140 Mbit/s picture telephony, are conducted, whereby, however, narrow band signal switching devices and broadband signal switching devices (preferably comprising common control devices) are provided in the switching centers as disclosed in the German Pat. No. 24 21 002.
In conjunction with a broadband signal time-division multiplex switching device whose cross points are respectively utilized in time-division multiplex for a plurality of connections, it is known in the art to connect respectively two lines with the assistance of a gate element which is switched on and off by a cross point-associated storage cell formed by a bistable D flip-flop, whereby the cross point-associated storage cell whose clock input is supplied with a corresponding clock signal is driven in only one coordinate direction, at its D input (Pfannschmidt, "Arbeitsgeschwindigkeitsgrenzen von Koppelnetzwerken f/u/ r Breitband-Digitalsignale", Dissertation Braunschweig 1978, FIG. 6.7). In view of a time-division multiplex factor of about 4-8 obtainable given a bit rate of 140 Mbit/s and in view of the involved circuit technology thereby required, however, pure space switching devices are currently preferred for switching broadband signals, the connections extending via the individual cross points being only spatially separated therein from one another.
A pure broadband signal space switching arrangement can be fashioned as a crosspoint matrix in whose cross points the switching elements are respectively controlled by a cross point-associated holding storage cell driven in two coordinates by two selection decoders, namely a row decoder and a column decoder, whereby the holding storage cells are respectively selected by row and column decoders in order to write new connections in and to cancel old connections (Pfannschmidt, Op. cit. FIG. 6.4). In such a broadband space switching device, the object of the invention is then to disclose a manner for a particularly expedient selection of the correspondingly-fashioned cross points.